Space Probe, Perhaps with a Chunk of Asteroid, Returns to Earth Sunday
Earth return of Japan's Hayabusa asteroid probe and release of its sample capsule.
Credit: C. Waste and T. Thompson (NASA/JPL-Caltech)

A Japanese space capsule perhaps carrying the first ever sample from an asteroid is on track for a Sunday parachute landing in South Australia.

The Hayabusa spacecraft is on-target, nearing completion of a seven year round-trip sojourn to asteroid Itokawa - a $200 million technology demonstration mission undertaken by the Japanese Aerospace Exploration Agency (JAXA).

Ground teams in Australia are in final preparation, gearing up for the Hayabusa return, said Paul Abell, a planetary scientist from NASA?s Johnson Space Center in Houston and a member of the Hayabusa Science Team and one of four individuals on a contingency ground recovery team. [Graphic: How Japan's Hayabusa Asteroid Mission Worked]

?The mood here is very good. The [Hayabusa] trajectory correction maneuvers have gone very well and we are really getting ramped up now to prepare for our search and recovery operations,? Abell told ?There is a real air of optimism and excitement.?

Abell described the scene in Australia, with JAXA having roughly 60 people to help with the entire operation. Some of them have already been deployed to remote sites to observe the capsule as it comes in to Woomera. JAXA has set up special sensor stations to monitor the incoming sampling capsule.

?Our NASA team is basically four strong and we are here and ready to assist with recovery operations in the event of an off-nominal return/landing. There are about 20 Royal Australian Air Force personnel here as well, helping to coordinate the recovery operations at the Woomera Test Range,? Abell explained.

Woomera Prohibited Area

Flying high above the landing zone, the NASA-sponsored Hayabusa Re-Entry Airborne Observing Campaign is to record the re-entry and destruction of the spacecraft proper and also track the thermally-protected return capsule as it heads for terra firma.

Following its fireball fling with Earth?s atmosphere, the hope is that the sampling capsule safely parachutes down into a pre-determined ellipse within the Woomera Prohibited Area (WPA) ? a large zone of remote landscape dedicated to weapons-testing in central South Australia.

?The plan is to find the capsule, assess its condition, and then transport it back to the Range Control Center of the Woomera Test Range,? Abell said. ?Once there it will be examined briefly and then put on an airplane bound for Japan.?

In Japan, the capsule is to find a home at JAXA?s sample curatorial facility in Sagamihara, Japan. At that site, the capsule will be inspected in detail and then opened in a laboratory clean room.

JAXA?s Hayabusa team has done a tremendous job and they should get lots of credit, Abell said. ?It truly is a heroic effort on their part to bring the spacecraft back to Earth,? he concluded.

Abell said the Japanese mission has yielded a bonanza of technical and scientific information.

?Hayabusa has paved the way for future asteroid missions, both robotic and human,? Abell noted. The lessons learned from the JAXA effort will be useful for close proximity operations at selected asteroids and in designing spacecraft destined to survey those objects in the future.

?The data from Hayabusa of asteroid Itokawa has revolutionized asteroid science. We have a whole new paradigm now from which to work in trying to understand these small near-Earth asteroids,? Abell concluded.

Return capsule: empty promises?

In late 2005, Hayabusa studied asteroid 25143 Itokawa for roughly three months, transmitting outstanding imagery and science data about the object. During that time, two surface sample runs were carried out.

Although Hayabusa did make contact with asteroid Itokawa, the probe?s sampling device failed to successfully operate.

Is it possible that the spacecraft?s return capsule is coming home empty of precious cargo??

?This is a very difficult question to answer,? explained JAXA?s Hitoshi Kuninaka, during a June 8 media briefing hosted by the Australian Science Media Center. He is one of the most senior members of the Hayabusa project team currently in Australia in preparation for the capsule?s return to Earth.

Kuninaka pointed out that the asteroid?s surface gravity is so low that scientists think the spacecraft kicked up material on contact with Itokawa, with bits of the asteroid drifting into the sample container.

Grains of dust will speak volumes

Also anxiously awaiting Hayabusa?s return in Australia is NASA?s Michael Zolensky, curator of stratospheric dust in the Astromaterials Research and Exploration Science directorate at Johnson Space Center.

Zolensky said that there?s good reason to expect that just the process of landing on the asteroid would have coated the inside of the spacecraft with dust. If so, even microscopic grains of dust will speak volumes.

?In fact, Hayabusa is probably going to return less than a gram of sample, at the most a few grams?possibly much less than that,? Zolensky advised. Nevertheless, an incredible amount of science can be done with a sample that small. A harvest of even just a sand-sized amount of material would be a fantastic treasure trove for scientists to examine, he said.

For a year, a team of largely Japanese scientists and some researchers from other countries will be studying the samples prior to their release to ?anyone on the planet who is qualified to study them,? Zolensky observed.

A robotic Apollo 13

In many ways, Hayabusa is a robotic equivalent to the Apollo 13 saga in which ground teams and onboard intelligence overcame a slew of technical snafus to return the aborted mission home.

For the Japanese probe, it has endured malfunctioning reaction wheels used to stabilize the craft?s attitude, a fuel leak of its chemical engine, loss of communications for over seven weeks, and woes with its ion engine propulsion system.

JAXA?s Kuninaka flagged the fact that Hayabusa?s Earth return was originally slated for 2007.

That extra time in limping home adds up to several last-minute worries.

Will the devices that need to fire to separate the landing capsule from Hayabusa function? This event is to occur three hours prior to reentry at some 40,000 kilometers distance from Earth.

Another nail-bitter is whether the sample capsule can then perform self-generated duties, such as parachute deployment.

?Yes, we have concerns,? Kuninaka said.

Leonard David has been reporting on the space industry for more than five decades. He is past editor-in-chief of the National Space Society's Ad Astra and Space World magazines and has written for since 1999.